This invention relates to an automatic sharp pencil and more particularly to a knock type sharp pencil provided in its outer cylinder with a core holding mechanism having an ability to move a core forwardly by a given length when a knock portion is pushed.
In such kind of conventional sharp pencil heretofore proposed, an engagement surface for defining the front end of a movable range of a chuck ring is formed by a step portion arranged in the inner surface of the outer cylinder. As a result, in order to deliver the core by a given length, it is necessary to work the outer cylinder with a high precision and accurately define the position where the core holding mechanism is secured to the outer cylinder.
In another conventional sharp pencil heretofore proposed, a chuck ring of a lead chuck is enclosed in a threaded cylinder which is operative to firmly connect a mouth piece to an outer cylinder. In addition, the chuck ring is axially moved in the threaded cylinder and provision is made of an air gap for defining the length of the core gripped by the lead chuck. As a result, such conventional sharp pencil is required to provide a large number of parts, complex in construction and troublesome in assembling. Particularly, such conventional sharp pencil is required to provide a chuck ring of a lead chuck composed of a connected ring and use a bonding step of connecting the mouth piece to the outer cylinder. As a result, the required number of parts becomes large.